Nemanja Vidic is suspended and both Gary Neville and Wes Brown have been ruled out already. And after victory over Blackburn, Ferguson seems certain to be without Jonny Evans, who limped off immediately after Cristiano Ronaldo's matchwinner.
It means Ferguson is now crossing his fingers that John O'Shea recovers from a sore heel in time to play against Jose Mourinho's side at the San Siro.
"It is a nightmare," admitted the United chief.
"Somewhere I have to find two centre-backs but it is looking very doubtful because Jonny is unlikely to play now."